It is well known in the motor vehicle arts that the rate of mechanical wear on the engine depends in part on the lubricating ability of the oil that is used to lubricate the engine parts, (sometimes referred to as “engine oil” or “motor oil”). The lubricating ability of these oils degrades as the engine is operated over time. In order to prevent catastrophic failures, there are various tests and guidelines for determining when an engine oil should be changed. Because of the range of conditions under which an engine may be operated, however, it is more reliable to test the oil in question than to rely solely on guidelines to determine when an oil should be changed.
The quality of an oil sample taken from the engine indicates whether the oil has degraded beyond suitability for continued use. Various methods for assessing the quality of an oil sample have been standardized and are known. It is common to obtain an oil sample from the oil pan of the engine after the engine has been running, so that the assessment is performed on a sample that is representative of the overall oil quality. Because the oil pan is beneath the engine block, however, it is not readily accessed.
Currently, oil samples are obtained using a variety of techniques and devices. Some devices obtain fluid through the drain opening. These devices rely on gravity flow, but require access to the underside of the engine, which is relatively difficult.
Other devices obtain fluid through the dipstick tube, which does not require access to the underside of the engine. Because they cannot rely on gravity flow, however, these devices require means for drawing the oil up out of the oil reservoir. This may take the form of a reversible plunger mechanism, such as in the device shown in FIG. 1. In the device shown in FIG. 1, a rigid plunger is manually retracted using a finger loop, which in turn draws oil into an opening at the remote end of an oil sampling tube, as indicated by the arrows. When the desired amount of oil has been withdrawn, it is released into a sample collector (not shown) by using a spring-loaded ratchet mechanism to return the plunger to its original position. Because the sampling tube must fit within the dipstick opening, its inside diameter is relatively small. This means that, depending on the required sample size, the distance through which the plunger must be withdrawn can be relatively great.
Because of shortcomings with the afore-mentioned device, the available technology for obtaining an oil sample remains less than satisfactory. In some devices, such a those that use spring-loaded suction for withdrawing oil from the oil plan, the oil discharge mechanism may leave some oil clinging to the inside of the sample tube. This can contaminate the subsequent sample, resulting in a false reading or analysis. In addition, the combined length of the plunger, handle, and sample tube can be well over four feet, making the device difficult to handle. Still further, the plunger, when it has been retracted, is susceptible to buckling when force is applied to return it to its starting position. Thus, there is a need for a sampling device that avoids cross-contamination of samples and is compact and easy to use.